I have had issues with logs of Exchange getting 100GB and more, or the backup application not clearing the logs. So, there is a way to keep the logs from getting large and you running out of diskspace. It’s a simple solution which you can undo it in 5 minutes with no repurcusions.

:: Open Exchange Management Console
:: Navigate to Organization Configuration/Mailbox
:: Right click on the Mailbox Database Store in question and select Properties
:: Click on the Maintenance tab and tick the option Enable Circular Logging
:: Click Apply
:: Dismount and Re-Mount Store

Downside to this? You can’t restore with current data. You can only restore from your last backup. Old log files are overwritten during this procedure and not enabled by default for a reason. I enabled circular logging, backed up the server, and disabled circular logging and scheduled more frequent backups in order to keep the log files under control.